cmd/gc: avoid clobbering the AST in cgen_callmeth.

It confused the detection of init loops when involving
method calls.

Fixes #3890.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6620067

diff --git a/src/cmd/gc/gen.c b/src/cmd/gc/gen.c
index 780141567720797542b98bab831235f58e9a9552..4f5aa3c3a6b15a8c0b3ca96f890961058cec7c5f 100644 (file)
--- a/src/cmd/gc/gen.c
+++ b/src/cmd/gc/gen.c
@@ -509,22 +509,24 @@ ret:
 void
 cgen_callmeth(Node *n, int proc)
 {
+       Node n2;
        Node *l;
 
-       // generate a rewrite for method call
+       // generate a rewrite in n2 for the method call
        // (p.f)(...) goes to (f)(p,...)
 
        l = n->left;
        if(l->op != ODOTMETH)
                fatal("cgen_callmeth: not dotmethod: %N");
 
-       n->op = OCALLFUNC;
-       n->left = n->left->right;
-       n->left->type = l->type;
+       n2 = *n;
+       n2.op = OCALLFUNC;
+       n2.left = l->right;
+       n2.left->type = l->type;
 
-       if(n->left->op == ONAME)
-               n->left->class = PFUNC;
-       cgen_call(n, proc);
+       if(n2.left->op == ONAME)
+               n2.left->class = PFUNC;
+       cgen_call(&n2, proc);
 }
 
 /*

diff --git a/src/cmd/gc/sinit.c b/src/cmd/gc/sinit.c
index 8e943e45a1ad48e5d473a7c83fe600ab2adab149..d1438f1003008d3bbc8a4fac320677cc32a86781 100644 (file)
--- a/src/cmd/gc/sinit.c
+++ b/src/cmd/gc/sinit.c
@@ -36,7 +36,9 @@ init1(Node *n, NodeList **out)
        init1(n->right, out);
        for(l=n->list; l; l=l->next)
                init1(l->n, out);
+
        if(n->left && n->type && n->left->op == OTYPE && n->class == PFUNC) {
+               // Methods called as Type.Method(receiver, ...).
                // Definitions for method expressions are stored in type->nname.
                init1(n->type->nname, out);
        }

diff --git a/test/fixedbugs/bug459.go b/test/fixedbugs/bug459.go
new file mode 100644 (file)
index 0000000..80abe5d
--- /dev/null
+++ b/test/fixedbugs/bug459.go
@@ -0,0 +1,35 @@
+// errorcheck
+
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 3890: missing detection of init loop involving
+// method calls in function bodies.
+
+package flag
+
+var commandLine = NewFlagSet() // ERROR "loop"
+
+type FlagSet struct {
+}
+
+func (f *FlagSet) failf(format string, a ...interface{}) {
+       f.usage()
+}
+
+func (f *FlagSet) usage() {
+       if f == commandLine {
+               panic(3)
+       }
+}
+
+func NewFlagSet() *FlagSet {
+       f := &FlagSet{}
+       f.setErrorHandling(true)
+       return f
+}
+
+func (f *FlagSet) setErrorHandling(b bool) {
+       f.failf("DIE")
+}